In order that glass fibers for use as textiles can be made economically, they must be produced and handled in groups of hundreds or even thousands. As is well known, glass is easily broken when its surface is scratched and the glass is stressed; and it is further known that glass surfaces when rubbed against each other will produce mutual abrasion of the surfaces. Immediately after being formed and before the individual fibers are brought together into a bundle or strand, therefore, the individual glass fibers must be coated with a protective material. Because the bundle or strands of glass fibers must be drawn over numerous guide surfaces at high rates of speed during the twisting, beaming, quilling, and weaving operations that are required of textiles, the sizes or coatings on the fibers must not only prevent mutual abrasion of the individual filaments but they must provide controlled tension to the fibers and be compatible with whatever subsequent treatment the fibers are to be given. No material has ever been found which is ideally suited as a coating material for glass fibers, and which will ideally fulfill all of the requirements and conditions to which the fibers are subjected before they end up as a finished product. The best overall material which the prior art has found has been a combination of starch and lubricants. The lubricants which have been used have been combinations of cationic lubricants which are soluble in the aqueous starch solution, and nonionic lubricants which appear to break up the starch film-forming materials and help in reducing the tensions that are developed when the bundle of fibers are drawn over guide surfaces in their dried condition. Attempts have been made to replace the starch with a synthetic polymeric film former because of the greater uniformity of such materials, but none have been developed to applicants' knowledge which are better than starch. Synthetic polymers generally suffer from the failing of producing too high tensions when the bundles are drawn over the guide surfaces. Starches, on the other hand, are not permanent film formers which can be depended upon to protect the fibers during their ultimate useage, and so the starches must be burned off of the fibers after they have been processed through the weaving operation. The burning process of most starches usually leaves a minor amount of black and objectional residue prior to the time that a finish coating of polymeric material is put onto the fibers as a protective coating for the fibers during their ultimate use. Ideally, a finish material which could also be used as a protective coating during the forming and twisting, quilling, beaming, and weaving operations and which did not have to be removed or replaced has been the ultimate objective of the art, but such a material or composition has not been found.
An object of the present invention is the provision of a new and improved coating material for glass fibers which will provide the desired protection and tension during the forming, twisting, quilling, beaming, and weaving operations, and which can be burned off of the fibers better than the prior art materials.
Another object of the present invention is the provision of a new and improved material of the above described type which not only provides good burn off, but which produces a film on glass fibers having the desirable characteristics of starch.
Another object of the present invention is the provision of a new and improved type of film former for glass fibers and method of making the same, which will allow the film former to be better tailored to the particular processing operations to which the glass fibers are to be subjected.
Further objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments and the accompanying claims.